Spatial data infrastructure

A spatial data infrastructure (SDI) is a data infrastructure implementing a framework of geographic data, metadata, users and tools that are interactively connected in order to use spatial data in an efficient and flexible way. Another definition is "the technology, policies, standards, human resources, and related activities necessary to acquire, process, distribute, use, maintain, and preserve spatial data".[1]

A further definition is given in Kuhn (2005):[2] "An SDI is a coordinated series of agreements on technology standards, institutional arrangements, and policies that enable the discovery and use of geospatial information by users and for purposes other than those it was created for."

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Some of the main principles are that data and metadata should not be managed centrally, but by the data originator and/or owner, and that tools and services connect via computer networks to the various sources.[3] A GIS is often the platform for deploying an individual node within an SDI. To achieve these objectives, good coordination between all the actors is necessary and the definition of standards is very important.

Due to its nature (size, cost, number of interactors) an SDI is usually government-related. An example of an existing SDI is the National Spatial Data Infrastructure (NSDI) in the United States. At the European side, INSPIRE is a European Commission initiative to build a European SDI beyond national boundaries and ultimately the United Nations Spatial Data Infrastructure (UNSDI) will do the same for over 30 UN Funds, Programmes, Specialized Agencies and member countries.

A SDI should enable the discovery and delivery of spatial data from a data repository, via a spatial service provider, to a user. As mentioned earlier it is often wished that the data provider is able to update spatial data stored in a repository. Hence, the basic software components of an SDI are:[3]

Software client - to display, query, and analyse spatial data (this could be a browser or a desktop GIS)

Catalogue service - for the discovery, browsing, and querying of metadata or spatial services, spatial datasets and other resources

Spatial data service - allowing the delivery of the data via the Internet

Besides these software components, a range of (international) technical standards are necessary that allow interaction between the different software components.[3][4] Among those are geospatial standards defined by the Open Geospatial Consortium (e.g., OGC WMS, WFS, GML etc.) and ISO (e.g., ISO 19115) for the delivery of maps, vector and raster data, but also data format and internet transfer standards by W3C consortium.

Geoportal Server is an open source solution for building SDI models where a central SDI node is populated with content from distributed nodes, as well as SDI models where each node participates equally in a federated mode.